Snap acting thermal disc with bent-over angulated leaf spring contact member



y 2, 1967 J. D. BOLESKY 3,317,693

SNAP ACTING THERMAL DISC WITH BENT-OVER ANGULATED LEAF SPRING CONTACTMEMBER Filed Oct. 21, '1964 FIG! 48 47 26 l5 FIG.3

INVENTOR JOHN D. BOLESKY 7770 3 1b ATTORNEYS United States Patent Oflice3,317,693 Patented May 2, 1967 3 317 693 SNAP ACTING THERNIAIJDISC WITHBENT-OVER ANGULATED LEAF SPRING CONTACT MEM- BER John D. Boleslty,Mansfield, Ohio, assignor to Therm-O- Disc, Incorporated, Mansfield,Ohio, a corporation of Ohio Filed Oct. 21, 1964, Ser. No. 405,416Claims. (Cl. 200-138) This invention relates to a thermostatic controland more particularly to a new and improved thermostatic control for useon small appliances having increased current carrying capacity.

Heretofore, in small thermostatic cont-r01 designed to carry relativelyhigh currents, it has been the practice to employ a mobile bridgingcurrent carrying member between two widely separated stationarycontacts. Although satisfactory from a current carrying standpoint, suchthermostatic controls were subject to contact contamination which wasgreatly enhanced due to the presence of two contact breaks.

The alternative was to furnish a control embodying a single contactbreak by providing a cantilevered arm on the end of which was mounted amobile contact which would make or break contact with a stationarycontact in response to the movements of the arm. The use of suchstructure was confined to relatively large devices by reason of the factthat the arm required to carry the desired current was too heavy to bendor flex within the confines of a small sized control. Accordingly, suchattempts have, until now, been only partially successful, for thereexisted problems in adequately securing the fixed end of thecantilevered arm and by the inability of the arm to bend enough inresponse to a small force to separate the contacts with a snap action.

In the present invention the cantilevered arm is formed by bending astrip of metal with an offset portion, securing the end of the offsetportion in a suitable housing, and mounting on the free end of the armthe mobile contact member. The offset portion in the strip serves toposition the fixed end of the cantilever arm, or the bend in the strip,closely adjacent the inside wall of the housing. This arrangement hasthe advantage that maximum deflection of the free end of the cantileverarm is obtained by applying a force along the arm at a specifieddistance from the inner wall of the housing nearest the fixed end of thearm. The force required in the device of the present invention issubstantially reduced to effect operation of the switch elements overthat used in previous devices. Thus, the arm will be responsive to amore sensitive temperature sensing device.

It is among the objects of this invention to provide a relatively smallthermostatic control of high current carrying capacity employing acantilevered contact carrying arm which is so mounted as to obtain themaximum deflection with the minimum amount of applied force.

It is a further object of this invention to provide a small thermostaticcontrol of relatively high current carrying capacity employing a singlecontact break and thus minimizing failure in operation due to contactcontamination.

These and other objects and advantageous features of the presentinvention will become apparent from the following detailed descriptionof a preferred embodiment thereof, taken in conjunction with theaccompanying drawings wherein corresponding reference characters denotecorresponding parts and wherein:

FIGURE 1 is a top plan view of a thermostatic control embodying thepresent invention;

FIGURE 2 is an enlarged top plan view of the device with thethermostatic element and retaining member therefor removed;

FIGURE 3 is a longitudinal sectional view taken on the line 3-3 ofFIGURE 2, illustrating the elements of the device in closed circuitposition;

FIGURE 4 is a transverse sectional view taken on the line 44 of FIGURE3;

FIGURE 5 is a side elevational detail view of the metal strip which hasbeen bent to form a cantilever arm upon which is mounted the mobilecontact;

FIGURE 6 is a perspective view of the elements of the switch containedin the device; and

FIGURE 7 is a top plan view of the blank from which the mobile contactcarrying arm of the switch is formed.

With reference to the accompanying drawings, there is illustrated athermostatically controlled device embodying a switch for controlling anelectrical circuit made in accordance with the teachings of the presentinvention and comprising a substantially cyclindrical housing 10 havinga bottom wall 11 and an upstanding side wall 12 extending therefrom,made preferably of an electrical insulating material which is heatresistant to a fair degree, such as a phenolic condensation product.Adjacent to its upper extremity the side wall 12 is provided with anoutwardly extended flange 13 forming a peripheral surface 14. Thehousing 10 defines a switch cavity designated by the numeral 15. Theupper surface of the bottom wall 11 serving as the bottom of the switchcavity 15 is formed with a semi-circular recess :16.

A separate end wall member 17 of suitable insulating material extendsacross the upper open end of the cavity 15 providing an arc shield orclosure for the open end of the switch cavity 15. The end wall member 17is substantially disc-like in contour and is provided with an inwardlyextending peripheral recess defining a horizontal wall 18 and a verticalwall 19. The portion of the end wall 17 defined by the vertical Wall 19seats within the cavity 15 and the horizontal wall 18 seats upon theupper end surface of the side wall 12. Formed in the top surface of theclosure of end wall member 17 is a recess 20, the peripheral edge ofwhich is offset to form a seat for the reception of bimetallic discmember 21.

A cup shaped metallic cover member 22 having a horizontal top wall 23and a downwardly extending vertical side wall 24 encompasses the upperportion of end wall member 17 and serves to maintain the disc and endwall assembled on the open end of the housing 10. A circular opening 25having a diameter approximately equal to that of the recess 20 of theend wall member 17 below is formed in the top wall 23 to permit the freemovement of the disc member between opposite positions of concavity. Thelower surface of the top wall 23 surrounding the opening 25 bearsagainst the upper surface of the bimetallic disc 21, maintaining thesame seated on the peripheral edge of the recess 20. The lower portionof the side wall 24 is depressed inwardly under the flange 13 andagainst the outer surface of the side wall 12 so as to fasten the covermember 22 securely to the housing 10, as shown in FIGURE 3.

Mounted in the cavity 15 of the housing are the switch elements of thedevice comprising a mobile contact carried by a cantilever mounted armand a fixed contact. A strip 26 of suitable, electrically conductingmetal, shown in the form of a blank in FIGURE 7, consists of twosegments 27 and 28. The side 28a of segment 28 departs from thedirection ofthe parallel sides of segment 27 by an angle shown in FIGURE7 as 45". The cantilever arm carrying the mobile contact is thus formedby bending the two segments of strip 26 about a fold line 29, as shownin FIGURE 7, to form the contact carrying arm 27 and anchoring segment28. The strip 26 in its bent or folded position is shown in FIGURES and6, the arm 27 and segment 28 being folded through an angle less than180. The segment 28 is folded slightly about line 30, for a purposewhich will be made clear hereinafter. The remaining perimeter of segment28, as shown in FIGURE 7, consists of a circular arc whose radius isequal to or only slightly smaller than that of the switch cavity andwhich ends at a short, straight-line portion of the circumference whichcontinues until it meets at right angles the edge of arm 27.

The folded metal strip 26 is disposed in the switch cavity 15 andsecured in the position shown in FIGURE 2 by terminal post 31 whichextends up through appropriate openings 32 and 33 in the bottom wall 11and anchoring segment 28, respectively.

A stationary contact arm 34, shown in FIGURE 6, consists of a lowerhorizontal portion 35, and an upwardly extending vertical portion 36which terminates in a horizontal-portion 37, the under surface of whichis provided with a contact surface. The perimeter of portion 35 consistspartly of a circular are 38 whose radius is equal to or only slightlysmaller than that of the switch cavity 15. At one end of arc 38 astraight-line segment 39 begins, to be joined at its end by circular arcsegment 40, having a radius smaller than that of are 38. The perimeterof portion 35 is completed by a straight-line segment 41 connecting arcs38 and 40'.

The vertical portion 36 of the arm 34 which is rectangular in shape, isbent horizontally at its upper extremity to form the contact engagingportion 37, which is arranged to extend over the mobile contact carryingarm 27.

The stationary contact arm 34 is mounted in the recess 16 formed in thebottom wall of the switch cavity 15 and secured in the position shown inFIGURE 2 by a terminal post 42 extending upwardly through appropriateopenings 43 and 44 in the bottom wall 11 and the portion 35,respectively. Opening 44 is concentric with the circular are 40. In theembodiment shown openings 32 and 43 in which the terminal posts aremounted are diametrically opposite to each other in the switch cavity15.

With the mobile contact carrying arm 27 and the fixed contact arm 34thus positioned, as illustrated in FIGURE 2, the upper horizontalcontact portion 37 of the stationary contact arm is directly above thecontact member 45 mounted on the end of the 'mobile contact carrying arm27. As the strip has been folded through an angle of less than 180*", aspreviously mentioned, the arm 27 is biased upwardly at an angle towardthe contact 37, causing the mobile contact 45 normally to be in contactwith the lower surface of contact portion 37.

In the operation of the thermostatic control, a bumper member 47,cylindrical in contour, upon the ends of which are formed sphericalbearing portions, extends through a suitable opening 48 in the end wallmember 17. The lower spherical bearing portion of the bumper 47 engagesan elevated surface 49 formed on the arm 27 which surface also serves tostiffen the arm 27 at its central portion and shifts the point ofgreatest flexing in the arm 27 to the fold 29. When the bimetallic disc21 is curved so that its upper surface is in one position of concavity,as shown in FIGURE 3, the bumper member 47 is freely slidable within theopening 48. Upon a rise in temperature to a critical point, the disc 21snaps to its opposite position of concavity, forcing the bumper 47 toengage the arm 27 and pivot the same about the fold line 29, breakingthe electrical contacts 45 and 37 and opening the electrical circuit.

The fold of less than 180 which is made in strip 26 along the line 29 issuch that the contact carrying arm 27 will support the weight of thebumper 47 and still leave the arm biased sufficiently toward thestationary contact that contact button 45 will bear firmly against theunderside of contact 37 when the circuit is in the closed position. Theelastic properties of the strip 26, however, are such that when the disc21 snaps, the contacts 45 and 37 will be separated with a snap actionminimizing arcing therebetween. By placing a deviation of 45 from thelongitudinal center line of the segment 28 as shown in FIGURE 7 (anangle which remains after the two segments are folded about line 29),the maximum free space between the arm 27 and the upper surface ofbottom wall 11 is obtained, permitting maximum deflection of the arm 27.The slight bend which has been placed in segment 28 along line 30 servesto bias the segment 28 against the bottom surface of the switch cavityand to exert pressure adjacent the fold line 29' when the arm 27 is inposition, thereby obtaining uniformity in the assembly of the devices.

Electrical terminal straps 50 and 51 are connected electrically withmobile contact 45 and stationary contact 37, through terminal posts 31and 42, respectively, as shown in FIGURE 3. The terminal straps 50 and51 may be of whatever shape, length, width, and thickness desired, buttypical members are shown in FIGURE 1.

Appropriate recesses 52 and 53 in the bottom exterior surface of thehousing 10 permit the heads of the terminal posts 31 and 42,respectively, to be flush with the surface of the housing, thusproviding a fiat mounting surface on the control to facilitate its usein appliances.

While there has been described herein and illustrated in theaccompanying drawings a presently preferred embodiment of the presentinvention, it is to be understood that various modifications andrefinements which depart from the illustrated embodiment may be adoptedwithout departing from the spirit and scope of the invention.

I claim:

1. A thermostatic control device comprising a hollow cylindrical housinghaving an open end and a closed end, diametrically opposed terminalsprojecting through the closed end of said housing into the housingchamber, switch means mounted within the housing chamber including afixed contact positioned circumferentially between said terminals, amobile contact mounted on a contact carrying arm extending diametricallyfrom said fixed contact, said mobile contact carrying arm having anoffset portion securing the same to one of said terminals, said mobilecontact carrying arm having a portion thereof reversely bent along atransverse line and angulated circumferentially from the plane of thearm to one of said terminals and secured thereto, said angulated portionhaving a fold therein to bias the arm against the closed end wall atsaid transverse line, and a snap acting thermostatic disc mounted in theopen end of said housing and having two positions of stability, saidthermostatic disc passing automatically from its first position ofstability to its sec-0nd position upon a rise in temperature of apredetermined degree and in its second position adapted to move saidmobile contact member with respect to said fixed contact member.

2. A thermostatic control device comprising a housing defining a switchchamber having a closed end and an open end, switch means mounted withinsaid switch chamber including a fixed contact, and a mobile contactadapted to engage the fixed contact, means for supporting said mobilecontact comprising a cantilever mounted arm spanning substantially thediameter of the switch chamber, said arm having an offset portionreversely bent along a transverse line and angulated from the plane ofthe arm and secured to a terminal post circumferentially spacedtherefrom, said angulated portion having a fold therein to bias the armagainst the closed end wall at said transverse bend, and means mountedin the open end of said switch chamber including a bimetallic memberhaving two opposite positions of stability and en gageabl e with saidcantilever mounted arm in one of said positions to move the mobilecontact with respect to the fixed contact.

3. A thermostatic control device comprising a hollow cylindrical housingdefining a switch chamber having an open end and a closed end,circumferentially spaced terminal members extending through the closedend of the housing, switch means disposed within said chamber includinga fixed contact operatively connected to one of said terminal members, amobile contact carrying arm connected to the other of said terminalmembers, said arm having a portion circumferentially offset from saidsupporting terminal and reversely bent along a transverse line andtraversing diametrically the switch chamber between said spaced terminalmembers and carrying a mobile contact engageable with the said fixedcontact, said arm having a fold therein to bias the arm against theclosed end Wall of the switch chamber at said transverse line, a snapacting thermostatic disc mounted in the open end of said housing andhaving two positions of stability, said thermostatic disc passingautomatically from its first position of stability to its secondposition upon a rise in temperature of a predetermined degree, saidthermostatic disc in its second position arranged to move said mobilecontact member with respect to said fixed contact member.

4. A thermostatic control device comprising a hollow cylindrical housinghaving an open end and a closed end, diametrically opposed terminalsprojecting through the closed end of said housing into the housingchamber, switch means mounted Within the housing chamber including afixed contact positioned circumfere-ntially between said terminals, amobile contact mounted on a contact carrying arm extending diametricallyfrom said fixed contact, said mobile contact carrying arm having aportion thereof reversely bent along a transverse line and angulatedfrom the plane of the arm to one of said terminals and secured thereto,said angulated portion having a fold therein to bias the arm against theclosed end at said transverse line, a closure member mounted in the openend of said chamber, a snap acting therm'o static disc mounted on theouter surface of said closure member and having two positions ofstability, said ther mostatic disc passing automatically from its firstposition of stability to its second position upon a rise in temperatureof a predetermined degree, and means carried by said closure member fortranslating movement of said disc to the mobile contact carrying arm.

5. A thermostatic control device comprising a hollow cylindrical housingdefining a switch chamber having an open end and a closed end,circumferentially spaced terminal members extending through the closedend of the housing, switch means disposed within said chamber includinga fixed contact, an offset member for operatively connecting said fixedcontact to one of said terminals, a mobile contact adapted to engagesaid fixed contact, a cantilever mounted arm extending diametrically ofsaid switch chamber for supporting said mobile contact, said arm havinga portion reversely bent along a transverse line and having an angulatedportion which is secured to the other of said terminals, said angulatedportion having a fold therein to bias the arm against the closed end atsaid transverse line, a closure member mounted in the open end of saidswitch chamber, a snap acting thermostatic plate passing automaticallyfrom its first position of stability to its second position upon a risein temperature of a predetermined degree, and means carried by saidclosure member for translating movement of said disc to the mobilecontact carrying arm.

References Cited by the Examiner UNITED STATES PATENTS 2,507,381 5/1950Morse 200-159 X 2,954,447 9/1960 Bolesky et a1. 3,014,105 12/1961Schmitt 200113 X 3,073,934 1/ 1963 Oakman et a1 200-159 BERNARD A.GILHEANY, Primary Examiner. T. MACBLAIN, H. A. LEWITTER, AssistantExaminers.

2. A THERMOSTATIC CONTROL DEVICE COMPRISING A HOUSING DEFINING A SWITCHCHAMBER HAVING A CLOSED END AND AN OPEN END, SWITCH MEANS MOUNTED WITHINSAID SWITCH CHAMBER INCLUDING A FIXED CONTACT, AND, A MOBILE CONTACTADAPTED TO ENGAGE THE FIXED CONTACT, MEANS FOR SUPPORTING SAID MOBILECONTACT COMPRISING A CANTILEVER MOUNTED ARM SPANNING SUBSTANTIALLY THEDIAMETER OF THE SWITCH CHAMBER, SAID ARM HAVING AN OFFSET PORTIONREVERSELY BENT ALONG A TRANSVERSE LINE AND ANGULATED FROM THE PLANE OFTHE ARM AND SECURED TO A TERMINAL POST CIRCUMFERENTIALLY SPACEDTHEREFROM, SAID ANGULATED PORTION HAVING A FOLD THEREIN TO BIAS THE ARMAGAINST THE CLOSED END WALL AT SAID TRANSVERSE BEND, AND MEANS MOUNTEDIN THE OPEN END OF SAID SWITCH CHAMBER INCLUDING A BIMETALLIC MEMBERHAVING TWO OPPOSITE POSITIONS OF A STABILITY AND ENGAGEABLE WITH SAIDCANTILEVER MOUTED ARM IN ONE OF SAID POSITIONS TO MOVE THE MOBILECONTACT WITH RESPECT TO THE FIXED CONTACT.